1. Field of the Invention
The present invention relates to a small stacked filter usable in radio communication equipments such as cellular (portable) phones.
2. Description of the Related Art
It has been known that resonators are formed by using strip conductors, and a plurality of these resonators are coupled to each other to configure a filter. For example, Japanese Unexamined Patent Application Publication No. 6-216605 discloses a strip line filter where resonators constructed of strip conductors are arranged in a plane direction and interdigital coupled to each other. Meanwhile, miniaturization and higher performance of radio communication equipments such as cellular phones are advanced in the recent years, and there is a demand for miniaturization of filters mounted thereon. The abovementioned strip line filter has difficulties in miniaturization because the resonators are planarly configured. As a filter advantageous in miniaturization, there is, for example, a stacked filter where conductors for resonators are stacked in the inside of a dielectric substrate, as disclosed in Japanese Patent No. 3067612.